One thing some engineers forget about when designing a sheet metal part is the material grain direction. During the fabrication process, most of the time, the sheet of metal will go through a line grain machine prior to forming, hardware, and finish. Line grain can also be known as Satin Finishing, Metal Brush Finishing, and Time Saver Finishing. Line grain is a uniform linear sanded finish that is used to remove and minimize scratches, blemishes, material defects, and mill scale.
During the engineering and design phase, it is important for engineers to keep the line grain direction in mind, especially for parts that get formed. There have been numerous times where the prints call out the wrong direction for the grain or the print doesn’t specify the direction at all. These both can lead to the following fabrication problems:
- Wrong direction called-out: if the grain on the print says to go parallel with the direction of the bend, this can cause the material to crack in the grain of the bend, especially if the material is thicker.
- No direction called-out: in a larger size fabrication shop where there are multiple fabricators working of a project, someone can mistakenly put the material in the line grain in the wrong direction, which causes the part to crack.
It is extremely important to list all information including the grain direction on the print. Since fabricators manufacture parts to print, it is critical to call it out properly on the print to prevent cracking issues. The line grain must run perpendicular to bend. In cases where there are multiple bends in a part that run in different directions, causing the line grain to run parallel with the bend, it is best to look at the material thickness and the size of the radius to limit any cracking.
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